Chromatic dispersion compensation

Abstract

A device (10;150;200) is configured to receive an optical signal. The device comprises a dispersion compensator (210a) comprising a plurality of optical dispersion compensator units (220). Each optical dispersion compensator unit comprises a plurality of delay elements (20;40). The dispersion compensator (210a) is configured to selectively activate one or more of the optical dispersion compensator units (220). The dispersion compensator (210a) is configured to compensate for dispersion of the optical signal with the activated one or more optical dispersion compensator unit (200).

The invention claimed is: 
     
       1. A device configured to receive an optical signal, the device comprising:
 a dispersion compensator comprising a plurality of optical dispersion compensator units,
 wherein each optical dispersion compensator unit comprises a plurality of delay elements, and 
 the dispersion compensator is configured to selectively activate one or more of the optical dispersion compensator units, 
 wherein the dispersion compensator is configured to compensate for dispersion of the optical signal with the activated one or more optical dispersion compensator units; 
 
 a polarization controller configured to output one or more optical signals to the dispersion compensator, wherein the or each optical signal has a single polarization; 
 wherein the polarization controller comprises a polarization module configured to receive an optical input signal and configured to convert a component having a first polarization mode into a converted component having a second, different, polarization mode; and 
 wherein the device further comprises a processing module configured to combine the converted component with a direct component received with said second polarization mode, wherein the processing module is configured to generate an optical output signal solely having said second polarization mode. 
 
     
     
       2. The device as claimed in  claim 1  wherein each of the plurality of delay elements is configured to apply a delay to a sub-band of the optical signal. 
     
     
       3. The device as claimed in  claim 2  wherein the sub-bands of the plurality of delay elements overlap in frequency. 
     
     
       4. The device as claimed in  claim 1  wherein the optical dispersion compensator unit is configured to apply a delay to the optical signal which varies linearly with frequency. 
     
     
       5. The device as claimed in  claim 1  wherein a said delay element is a micro-ring resonator. 
     
     
       6. The device as claimed in  claim 1  wherein the optical dispersion compensator unit comprises an optical bus to which one or more of the delay elements is coupled, wherein the optical signal is delayed by each of the plurality of delay elements. 
     
     
       7. The device as claimed in  claim 1  wherein the dispersion compensator comprises a first switch associated with each optical dispersion compensator unit, wherein the first switch is configured to be controllable to couple the optical signal with the associated optical dispersion compensator unit to activate the optical dispersion compensator unit. 
     
     
       8. The device as claimed in  claim 7  wherein the first switch is configured to selectively couple the optical signal with the associated optical dispersion compensator unit to activate the optical dispersion compensator unit or to couple the optical signal to an optical bus to bypass the optical dispersion compensator unit. 
     
     
       9. The device as claimed in  claim 7  wherein the first switch comprises a Mach-Zender interferometer. 
     
     
       10. The device as claimed in  claim 1  wherein the device comprises a first dispersion compensator and a second dispersion compensator, wherein the first dispersion compensator is configured to receive a first optical signal having a first polarization and the second dispersion compensator is configured to receive a second optical signal having a second polarization different to the first polarization,
 wherein each of the first dispersion compensator and the second dispersion compensator comprises the dispersion compensator as claimed in  claim 1 . 
 
     
     
       11. The device as claimed in  claim 1  wherein the processing module comprises a first optical phase shift module configured to apply a first phase shift to the converted component and/or direct component received from the polarization module, and
 the processing module further comprises a first optical coupler configured to receive the converted component and direct component, at least one of the converted component and direct component being phase shifted by the first phase shift, 
 wherein the first optical phase shift module is configured to apply the first phase shift such that the first optical coupler outputs a first and second optical signal of equal power. 
 
     
     
       12. The device as claimed in  claim 11  wherein the processing module comprises a second optical phase shift module configured to apply a second phase shift to the first and/or second optical signal received from the first optical coupler, and
 the processing module further comprises a second optical coupler configured to receive the first and/or second optical signal, at least one of the first and/or second optical signal being phase shifted by the second phase shift, 
 wherein the second optical phase shift module is configured to apply the phase shift such that the coupler outputs one or more optical signal solely having said first and/or second polarization mode. 
 
     
     
       13. A method of dispersion compensation of a received optical signal, comprising:
 configuring a dispersion compensator comprising a plurality of optical dispersion compensator units, wherein each optical dispersion compensator unit comprises a plurality of delay elements, 
 wherein configuring the dispersion compensator comprises selectively activating one or more of the optical dispersion compensator units, 
 such that the dispersion compensator compensates for dispersion of the optical signal with the activated one or more optical dispersion compensator units; 
 controlling a polarization of the received optical signal and outputting one or more optical signals to the dispersion compensator, wherein the one or more optical signals has a single polarization; 
 wherein controlling the polarization of the received optical signal comprises receiving an optical input signal and converting a component having a first polarization mode into a converted component having a second, different, polarization mode; and 
 combining the converted component with a direct component received with said second polarization mode, and generating an optical output signal solely having said second polarization mode. 
 
     
     
       14. The method as claimed in  claim 13  wherein a said delay element applies a delay to a sub-band of the optical signal. 
     
     
       15. The method as claimed in  claim 14  wherein the sub-bands of the plurality of delay elements overlap in frequency. 
     
     
       16. The method as claimed in  claim 13  wherein the optical dispersion compensator unit applies a delay to the optical signal which varies linearly with frequency. 
     
     
       17. The method as claimed  claim 13  wherein the optical dispersion compensator unit couples an optical bus to one or more of the delay elements, wherein the plurality of delay elements delay the optical signal. 
     
     
       18. The method as claimed in  claim 13  wherein the dispersion compensator comprises a first switch associated with each optical dispersion compensator unit, wherein the first switch is controlled to couple the optical signal with the associated optical dispersion compensator unit to activate the optical dispersion compensator unit. 
     
     
       19. A computer program product, comprising instructions which, when executed on at least one processing circuit, cause the at least one processing circuit to carry out the method according to  claim 13 . 
     
     
       20. A controller configured to control a device arranged to receive an optical signal, wherein the device comprises a dispersion compensator comprising a plurality of optical dispersion compensator units,
 the controller is configured to control a selective activation of one or more of the optical dispersion compensator units, such that the activated one or more optical dispersion compensator units compensates for dispersion of the optical signal; 
 the device further comprising a polarization controller configured to output one or more optical signals to the dispersion compensator, wherein the or each optical signal has a single polarization; 
 wherein the polarization controller comprises a polarization module configured to receive an optical input signal and configured to convert a component having a first polarization mode into a converted component having a second, different, polarization mode; and 
 wherein the device further comprises a processing module configured to combine the converted component with a direct component received with said second polarization mode, wherein the processing module is configured to generate an optical output signal solely having said second polarization mode.